I recently have dealt with a contractor who has rolls of wires that are mislabeled. The rolls are labels #14 THHN stranded. The actual labeling on the insulation says #16 type TFFN or MTW. I am not going to allow the wire to be used, but the insualtion sure looks like THHN. the insulation appears to be a bit thicker than #14 THHN but I'm not sure if this is just a variance that may occur in the manufacturing process. I easily spotted some THHN #16 this contractor accidently( I hope) used before, but this # 16 was hard to tell without reading the labeling on the insulation.

I have told the contractor to have his guys read the insulation not the roll but the accident happens anyways.

Several questions--

Has anyone seen this occurence of mislabeling?

Is there an easy way to determine all the different insulation types? some are fairly similar looking.

I am going to notify the manufacturer of this occurence and see if they have knowledge of a bad batch of labeled wire or if this could be an isolated incident.

And just in case anyone was asking themselves if the contractor might be trying to pull a fast one, I saw what appeared to be full rolls from the manufacturer, but you just never know.